Mercurial > hg > nginx-quic
view src/os/unix/ngx_gcc_atomic_amd64.h @ 4749:613750237b36
Entity tags: the "etag" directive.
It allows to disable generation of nginx's own entity tags, while
still handling ETags in cache properly. This may be useful e.g.
if one want to serve static files from servers with different ETag
generation algorithms.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Mon, 09 Jul 2012 14:53:42 +0000 |
parents | d620f497c50f |
children |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #if (NGX_SMP) #define NGX_SMP_LOCK "lock;" #else #define NGX_SMP_LOCK #endif /* * "cmpxchgq r, [m]": * * if (rax == [m]) { * zf = 1; * [m] = r; * } else { * zf = 0; * rax = [m]; * } * * * The "r" is any register, %rax (%r0) - %r16. * The "=a" and "a" are the %rax register. * Although we can return result in any register, we use "a" because it is * used in cmpxchgq anyway. The result is actually in %al but not in $rax, * however as the code is inlined gcc can test %al as well as %rax. * * The "cc" means that flags were changed. */ static ngx_inline ngx_atomic_uint_t ngx_atomic_cmp_set(ngx_atomic_t *lock, ngx_atomic_uint_t old, ngx_atomic_uint_t set) { u_char res; __asm__ volatile ( NGX_SMP_LOCK " cmpxchgq %3, %1; " " sete %0; " : "=a" (res) : "m" (*lock), "a" (old), "r" (set) : "cc", "memory"); return res; } /* * "xaddq r, [m]": * * temp = [m]; * [m] += r; * r = temp; * * * The "+r" is any register, %rax (%r0) - %r16. * The "cc" means that flags were changed. */ static ngx_inline ngx_atomic_int_t ngx_atomic_fetch_add(ngx_atomic_t *value, ngx_atomic_int_t add) { __asm__ volatile ( NGX_SMP_LOCK " xaddq %0, %1; " : "+r" (add) : "m" (*value) : "cc", "memory"); return add; } #define ngx_memory_barrier() __asm__ volatile ("" ::: "memory") #define ngx_cpu_pause() __asm__ ("pause")